This invention relates generally to refrigeration systems and, more particularly, to purge recovery systems for removing noncondensable gases from a refrigeration circuit.
Periodic purging of water and non-condensable gases from a refrigeration circuit is common in large chiller systems. This is commonly accomplished by a way of a so called "thermal purge", wherein the refrigerant and a mixture is caused to flow over a cooling coil to thereby condense the refrigerant from the mixture, with the remaining air then becoming more concentrated so that it can eventually be evacuated by way of a small vacuum pump. This process is enhanced by using a compressor to increase the pressure in the purge chamber, thereby increasing the amount of refrigerant that is condensed. However, even with this improvement there will still be some refrigerant in the non-condensing gases that have entered into the atmosphere. Not only is this a waste of refrigerant which must eventually be replaced, but it also contributes to the undesirable emissions to the Earth's atmosphere.
A further enhancement of the purge process is described in U.S. Pat. No. 4,984,431, assigned to the assignee of the present invention, wherein a carbon filter is placed in the venting circuit such that the discharge gases from the purge chamber pass into the charcoal filter where refrigerant is absorbed. Eventually, the non-condensable gases are released from the filter container and the container is then pumped down to remove the refrigerant from the filter and return it to the refrigeration circuit.
While this enhanced version of a purge system is capable of removing most of the refrigerant from the non-condensable gases prior to their being vented to the atmosphere, it is recognized that a failure within the system may cause an undesirable release of refrigerant to the atmosphere. For example, in the event that there is a loss of or reduction in the flow of coolant medium to the coil in the purge chamber as would occur, for example, if a refrigerant filter were plugged, or if there was dirt in the expansion orifice, or if the water supply were turned off, then the effectiveness of the purge chamber would be substantially diminished, or even curtailed, and would thereby permit the refrigerant to be vented with the non-condensable gases.
Another failure that could occur is that of the relief valve in the pressurized purge chamber. That is, if the relief valve, which is provided to release the non-condensable gases from the purge chamber, fails to open as intended, the purge chamber and the associated piping would become over-pressurized and a failure could occur. This would result in a substantial loss of refrigerant to the atmosphere. On the other hand, if the relief valve fails in the open position, such as would occur if a spring breaks, then the effect of a compression within the purge chamber would be negated and the degree of condensation would be substantially reduced. Again, this would result in increased quantities of refrigerant being vented to the atmosphere.
Another possibility for failure within the system is that of the solenoid valve which vents the storage tank, or in the case of the system of the above-mentioned patent, the carbon filter tank, to the atmosphere. If this valve fails to open as designed, the system can again become over-pressurized, in which case a rupture could occur to thereby allow the unpressurized flow of a refrigerant mixture from the carbon filter tank.
It is therefore an object of the present invention to provide an improved purge recovery system for a refrigerant circuit.
Another object of the present invention is the provision in a purge recovery system for fail-safe operation.
Another object of the present invention is the provision in a purge recovery system for a shut-down of the system in the event of certain predetermined undesirable conditions being detected.
These objects and other advanced features and advantages become more readily apparent upon reference to the following description when taken into conjunction with the appended drawings.